This invention relates to communication networks. In particular, this invention relates to digital wireless communication networks also known as digital cellular networks.
Digital cellular communication networks are well known. Instead of using an analog signal to modulate a radio frequency carrier, digitized and encoded information is modulated onto a radio frequency wave that is received, and information is recovered by decoding and converting the digital information back to an analog format.
Most digital cellular networks use so-called CDMA, TDMA or other encoding techniques to carry digital information between subscribers.
FIG. 1 shows a simplified block diagram of a prior art digital cellular communication system (10). A cellular service provider (12) provides wireless cellular communications service to subscribers that includes the ability to communicate between a portable or mobile cellular telephone subscriber unit (14) and other telephone users (16). A telephone call to a cellular subscriber (14) from a land-line telephone 16 is first routed through the public switched telephone network (PSTN) (18). By analyzing the called number, the PSTN (18) routes the call to equipment owned and operated by the cellular service provider (12) by analysis of the called number.
When an incoming call (20) to the cellular subscriber (14) is received at the switching equipment (22) of the cellular service provider (12), encoding circuitry (23) of the cellular service provider converts analog voice signals to a digital format. The encoded information is transmitted (24) across the cellular service provider""s network, being received by the cellular telephone (26) that is being called by the caller.
The called subscriber""s cellular telephone (26) includes within it circuitry to demodulate the radio frequency signal, decode the digital information therein, and reconstruct the original analog waveform of the caller""s voice so that a conversation can take place. The caller""s voice is reproduced whereby the path between the caller (16) and the called party (14) appears to be seamless.
A problem with prior art wireless cellular networks, however, is their inability to accommodate data transmission without first using a special dialing procedure to access special encoding circuitry. Facsimile machines (28, 32), which are commonly used to transmit documents, use audio frequency tones to transmit digitized images. The audio frequency tones used by facsimile machines (28, 32) are phase and amplitude modulated and the encoding circuitry (23) used to digitize voice information cannot properly encode tones from a fax machine. Similarly, tones used by modems to exchange data between computers are both phase and amplitude modulated.
To FAX a document over a digital wireless communications network, a caller with a fax to send to someone using a digital cellular phone network must dial a separate number of the cellular service provider that is equipped to accept calls from facsimile machines. After a call is placed to such a number, the phone number of the cellular service customer to whom the fax is addressed must then be entered in order to route the call to the proper phone. This two-step dialing procedure is cumbersome and requires the intervention of the caller.
Another method of providing fax capability to digital wireless subscribers is to allocate a separate number for the subscriber (26) to which is coupled encoding circuitry (30) for data transmissions. A drawback of this approach, however, is that for every subscriber, the cellular service provider must allocate two numbers: one number for voice frequency telephone calls and another number for facsimile transmissions.
A problem with these prior art digital cellular networks is their inability to automatically accommodate data transmissions, such as those from a fax machine but also including those that originate from a computer. Since voice signals are encoded using one technique and data signals are encoded using a different technique, a method and apparatus for automatically routing data calls to appropriate equipment needed to encode data would be an improvement over the prior art. Callers to a subscriber of wireless digital cellular service who wish to send data, i.e., either a fax or computer data, might be able to call one number that belongs to the cellular subscriber and have either a voice frequency exchange with the subscriber or send a fax or other data to the subscriber without having to dial a separate number. A cellular service provider could accommodate customers"" data transmissions automatically, without having to allocate separate numbers for data transmission.
An object of the present invention is to provide an automatic service selection technique for use with digital wireless networks whereby voice frequency signals and data signals can be automatically switched to appropriate encoding circuitry prior to transmission on the digital wireless network.
There is provided herein a method and an apparatus to automatically identify a call from a fax machine and upon the detection thereof to route the call to appropriate conversion circuitry for encoding facsimile machine data for transmission on a digital wireless network.
The invention is comprised of circuitry that monitors incoming or outgoing calls to or from a digital wireless subscriber for the presence of facsimile machine connect tones, the presence of which identifies the call as originating from a fax machine. If such tones are detected, the call is automatically routed to specialized circuitry capable of modulating fax machine tones. If facsimile machine control tones are not detected, audio signals for the call are routed to other circuitry used to digitize and encode voice signals.
In an alternate embodiment, computer modems equipped to produce other control tones can be recognized and used to identify the call as originating from a modem. In this case, other circuitry could be used to route computer data from a modem to other circuitry that is capable of encoding phase and amplitude modulated audio signals used with computer data.